Sandwich Structure for Thermoplastic Body-Panels with Class-A Surface by Injection Molding

Especially in horizontal applications of thermoplastic body-panels occurs a conflict between the required thermal stability (generally achieved with short glass fibers) and the high level surface finish as the reinforcements worsen the surface texture.

The sandwich-molding procedure for bigger body-panels, developed further at BMW, offers an innovative solution to this problem. Two materials, one with good surface finish properties (material A) and another with glass fiber reinforcement (material B), are coinjected in a single process step. The result is a part with class-A surface (only material A visible at the surface), advanced mechanical and thermal properties. Additionally to an outstanding surface finish the body-panel exhibits small thermal expansion relevant for reduction of gaps to bordering parts.